Side-chain quadruple H-bonds empower self-healing e-skins with ultralow-temperature tolerance
Polar exploration demands robotic systems capable of operating at extreme low temperatures, yet existing electronic skins (e-skins) fail due to polymer brittleness and impaired self-healing. Here, we report a supramolecular elastomer strategy that enables highly stretchable, self-healing, and sensitive e-skins functional at −78 °C. The elastomers are based on a poly(dimethylsiloxane) (PDMS) backbone (Tg = −127 °C, Tb = −150 °C) functionalized with kinetically reversible quadruple hydrogen-bonding motifs (2-ureido-4[1H]-pyrimidone, UPy) in side chains (S-UD) or main chains (M-UD). At −78 °C, S-UD elastomers exhibit superior stretchability, with optimized S-U1.2D0.8 achieving elongation at break of ~3257%, 3.4 times that of PDMS controls and exceeding M-U1.2D0.8 (~2474%). Self-healing efficiency after 24 h at −78 °C reaches ~75.9% for S-UD versus ~34.3% for M-UD, with visual scratch disappearance only in S-UD. Density functional theory (DFT) analysis reveals that S-UD possesses more thermodynamically favorable chain convergence, enhancing cryogenic self-healing. The optimized S-UD elastomer serves as an excellent substrate for constructing ultralow-temperature-tolerant e-skins, addressing a critical bottleneck in polar robotics.